In certain bulk materials handling equipment, such as the equipment described and illustrated in U.S. Pat. No. 5,051,041 and U.S. Pat. No. 5,355,993, a pump feeder moves bulk material through a housing from an inlet to an outlet by a rotating drive rotor having two or more drive disks mounted to or integral with a rotating hub. In the past, this type of equipment has been used for feeding coal and other breakable material having uniform and non-uniform gradation. Typically, the drive systems for this equipment have delivered large torque at slow speed.
As such equipment is adapted to handle different materials supplied in different sizes, problems that have not been encountered previously are arising. One such problem of major importance is the tendency of smaller size equipment, handling harder, smaller size material such as plastic, to stall, sometimes only temporarily, as the material being handled wedges between the rotating drive rotor and the housing or stationary parts mounted to the housing. This wedging of material can occur, for example, between the drive disks of the drive rotor and the housing inner wall or between the hub of the drive rotor and a materials scraper mounted to the inner wall of the housing.
Simply increasing the drive power (i.e., providing a larger drive motor) to overcome the wedging is not, in most instances, an adequate or satisfactory solution to the problem. Cost and space limitations are but two restrictions on simply providing increased drive power. Certain of the materials being handled are not easily breakable, so a larger drive motor merely increases the effect of the material wedging between the rotating drive rotor and the housing or stationary parts mounted to the housing. Thus, a larger drive motor can exacerbate the problem, resulting in a complete stoppage of operation and damage to the equipment. With breakable materials, such as coal, the drive torque is large enough to break or pulverize the material into smaller pieces that do not wedge between the rotating drive rotor and the housing or stationary parts mounted to the housing.
Although this adverse wedging effect might not be a regular occurrence and is likely to be different for handling different types of material, when it does occur, even temporarily, it affects accuracy and feeder performance to an unacceptable extent. Because the tendency of the equipment to stall, either temporarily or for longer periods of time, due to this wedging is greater at higher speed operation of the equipment, slowing down the operation of the equipment to reduce the likelihood of material wedging, while possibly reducing the likelihood of wedging, also is unacceptable.
To overcome the shortcomings of existing devices, a new bulk materials pump feeder is provided. An object of the present invention is to provide an improved bulk materials pump feeder that minimizes jamming of the disks. A related object is to prevent stall, even temporarily, caused as the material being handled wedges between the rotating drive rotor and the housing or stationary parts mounted to the housing. Another object is to avoid having to increase the drive power to overcome the wedging problem. It is still another object of the present invention to achieve these advantages within the confines of cost and space limitations. Yet another object of this invention is to provide a bulk materials pump feeder adapted to handle a wide variety of different materials supplied in different sizes. Additional objects are to achieve accuracy and assure optimal feeder performance.